Long press on a blank place on your homescreen display.
Look at the bottom and choose Themes.
Choose the theme you no longer want and there should be a delete option at the bottom of your screen as per the screenshot from my own Note 9.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help.
You don't have to delete any themes
At the very top of the galaxy store/my themes section all you have to do is make sure the check is on the 'default' theme
I was trying to figure this out for over an hour. I found this response and it helped tremendously! I couldn't figure out. I wanted to use night mode on my SNote 10 Plus and I couldn't use it without uninstalling the theme (Christmas theme of course lol). Thank you for your tip!!
That's the whole reason why I made the post! It took my like 2 days to figure it out because I wanted my phone on night mode as well.
Figured if i needed help others did too!